Many experiments involve collecting data in trials and varying one or
more parameters across trials. The ndata analysis system can help you
group trials together that share common parameter values. How trials
are grouped is determined by the second non-comment line in the nda
script, known as the grouping line.

The grouping line must take one of the following forms:

individual - process each trial separately, thus no grouping

all - use all trials.

group 0 - separate trials into as many groups as possible.

group 1 [var_param_1] - group on the named parameter, ignoring all
others.

group 2 [var_param_1] [var_param_2] - group on the two named
parameters, ignoring all others.

group [n] [var_param_1] ... [var_param_n] - ...

The names of parameters that vary across trials in the ndata file are
known as var params. The var param names can be determined by
using the ndata application program to browse the data file.